Genetic Hypervariability in Two Distinct Deuterostome Telomerase Reverse Transcriptase Genes and their Early Embryonic Functions
Bibliographic record
Abstract
Functional proteins of complex eukaryotes within the same species are rather invariant. A single catalytic component of telomerase TERT is essential for an active telomerase complex that maintains telomeres. Surprisingly, we have identified two paralogous SpTERT-L and SpTERT-S genes with novel domains in Strongylocentrotus purpuratus (purple sea urchin). The SpTERT-S and SpTERT-L genes were differentially expressed throughout embryogenesis. An unusual germline nucleotide substitution and amino acid variation was evident in these TERTs. The hypervariability of SpTERT-S haplotypes among different individuals reached unprecedented levels of pi > 0.2 in exon 11 region. The majority of nucleotide changes observed led to nonsynonymous substitutions creating novel amino acids and motifs, suggesting unusual positive selection and rapid evolution. The majority of these variations were in domains involved in binding of SpTERT to its RNA component. Despite hypervariability at protein level, SpTERT-S conferred telomerase activity, and its suppression during early embryogenesis led to arrest at late mesenchymal blastula. Domain exchange and embryo rescue experiments suggested that SpTERT may have evolved functions unrelated to classic telomerase activity. We suggest that telomerase has a specific and direct function that is essential for integration of early polarity signals that lead to gastrulation. Identification of these unique hypervariable telomerases also suggests presence of a diversity generation mechanism that inculcates hypervariable telomerases and telomere lengths in germline.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".